1. Field of the Invention
The present disclosure relates to medical imaging of small animals and more specifically to an enclosure for accommodating small animals while being imaged in an awake state.
2. Description of the Related Art
Motion of a living subject during medical imaging procedures can cause image artifacts. The sources of motion can vary and may include restlessness, scratching, respiration and heart beating, to small movements due to pressure changes over the cardiac cycle. In some cases, motion artifacts degrade the diagnostic value of an image, wasting significant time and money.
Efficient methods for testing new drugs are very important to the pharmaceutical industry. The ability to screen test subjects for effects of a particular drug is an essential element in the process of product development. Small animals are essential for pharmaceutical testing, and mice, in particular, are useful for modeling human diseases. Efforts to scale down clinical medical imaging systems for smaller subjects have allowed medical researchers to obtain high-resolution computed tomography (CT) images of small animals for disease studies. Noninvasive imaging techniques, such as X-ray, CT, and positron emission tomography (PET), have been developed for small animal medical imaging applications. For example, small animal imaging is currently being used in cancer research to monitor tumor growth and regression in mice.
While anatomical models are useful for studying drug effectiveness, it is very often desirable to screen test subjects for physiological effects of a drug. PET and single photon emission computed tomography (SPECT) are among current techniques used for functional medical imaging. Because animal test subjects must be kept awake during the screening process in order to monitor functional processes, either the animal must remain motionless for the duration of the scan or its movements must be tracked, measured and recorded with a high degree of precision and accuracy. Unrestrained awake animals tend to move around rapidly and present imaging challenges. Although sedation and physical restraint can be used to impede animal motion for this type of medical scan, both methods have the potential to alter the neurological and physiological processes that are being studied.
U.S. Pat. No. 8,170,302 “System and Method for Generating Motion Corrected Tomographic Images”, and United States Patent Application Publication Number 2008/0317313 “System and Method for Tracking Motion for Generating Motion Corrected Tomographic Images” both discuss the use of an enclosure or burrow to restrain an awake animal during imaging. Optical and reflective markers are adhered to the restrained but awake animal during imaging. Two or more cameras track the relative motion of the markers so that the animal's motion can later be accommodated for, and corrected, during image processing. The enclosure is optically transparent to the illumination wavelength and optically uniform so that the external images of the animal can be made without significant image distortion. A one-piece enclosure with optically uniform properties in the location of the optical and reflective markers can be challenging to manufacture.
Despite the teachings provided in the above publications, improvements to animal enclosures are needed in order to provide distortion-free images for motion tracking and further advance the art of small animal imaging for medical research.